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United States Patent |
5,550,885
|
Nam, ;, , , -->
Nam
,   et al.
|
August 27, 1996
|
Control device for power saving
Abstract
A control device for power saving for personal computers, printers, etc.
which generates a suspension signal or a power-off signal to perform power
saving by detecting input horizontal and vertical sync signals. The
suspension signal provides a suspension mode for a minimum basic operation
of the computer or printer, while the power-off signal provides a system
power-off mode. The control device is designed as a digital circuit
comprising latches, counters, monostable multivibrators, and other logical
elements. Integration of the circuit is possible as well as its transient
response characteristic is improved.
Inventors:
|
Nam; Keyoung T. (Kyungsangbuk-Do, KR);
Sung; Hong E. (Kyungsangbuk-Do, KR)
|
Assignee:
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LG Electronics, Inc. (KR)
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Appl. No.:
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563984 |
Filed:
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November 29, 1995 |
Foreign Application Priority Data
| Nov 30, 1994[KR] | P94-31938 |
Current U.S. Class: |
377/27; 327/544; 377/20 |
Intern'l Class: |
H03K 021/00 |
Field of Search: |
377/27,55-5-6,20
327/544
|
References Cited
U.S. Patent Documents
4994719 | Feb., 1991 | Lenardo | 315/411.
|
5329169 | Jul., 1994 | Ihara | 327/544.
|
Foreign Patent Documents |
000549165 | Jun., 1993 | EP | 327/544.
|
Primary Examiner: Wambach; Margaret Rose
Attorney, Agent or Firm: Fish & Richardson P.C.
Claims
What is claimed is:
1. A control device for power saving comprising:
horizontal sync signal input means for providing a horizontal sync signal
synchronized with a system clock signal;
horizontal sync signal detecting means for detecting whether or not said
horizontal sync signal is inputted by counting an output of said
horizontal sync signal input means;
horizontal detected signal output means for outputting a horizontal
power-off signal in accordance with an output of said horizontal sync
signal detecting means;
vertical sync signal input means for providing a vertical sync signal
synchronized with said system clock signal;
vertical sync signal detecting means for detecting whether or not said
vertical sync signal is inputted by counting an output of said vertical
sync signal input means;
vertical detected signal output means for outputting a vertical power-off
signal in accordance with an output of said vertical sync signal detecting
means;
control signal output means for outputting a system power-off signal or a
suspension signal for a suspension mode in accordance with said horizontal
power-off signal from said horizontal detected signal output means and
said vertical power-off signal from said vertical detected signal output
means; and
clock generating means for providing said system clock signal to said
horizontal sync signal detecting means and said vertical sync signal
detecting means.
2. A control device for power saving as claimed in claim 1, wherein said
horizontal sync signal input means comprises:
a first flip-flop for synchronizing said horizontal sync signal with said
system clock signal; and
a second flip-flop being toggled by said horizontal sync signal
synchronized by said first flip-flop and providing its inverting output
and non-inverting output to said horizontal sync signal detecting means.
3. A control device for power saving as claimed in claim 1, wherein said
horizontal sync signal detecting means comprises:
two counters for counting said system clock signal in a period when they
are not reset, said counters being reset by an output of said horizontal
sync signal input means;
two AND gates for resetting said counters in accordance with a system reset
signal and output of said horizontal sync signal input means;
two other AND gates and an OR gate for detecting said input horizontal sync
signal by combining outputs of said counters.
4. A control device for power saving as claimed in claim 1, wherein said
horizontal detected signal output means comprises:
a first monostable multivibrator providing a pulse signal in response to
the output of said horizontal sync signal detecting means;
a flip-flop receiving said pulse signal from said first monostable
multivibrator as its clock signal, and outputting said horizontal
power-off signal to said control signal in response to said horizontal
sync signal outputted from said first flip-flop in said horizontal sync
signal input means;
an inverter and an AND gate for resetting said flip-flop in accordance with
the output of said second monostable multivibrator.
5. A control device for power saving as claimed in claim 1, wherein said
vertical sync signal input means comprises:
a third flip-flop for synchronizing said vertical sync signal with said
system clock signal; and
a fourth flip-flop being toggled by said vertical sync signal synchronized
by said third flip-flop, said fourth flip-flop providing its inverting
output and its non-inverting output to said vertical sync signal detecting
means.
6. A control device for power saving as claimed in claim 1, wherein said
vertical sync signal detecting means comprises:
two counters for counting said system clock signal in a period when they
are not reset, said counters being reset by an output of said vertical
sync signal input means;
two AND gates for resetting said counters in accordance with a system reset
signal and output of said vertical sync signal input means;
two other AND gates and an OR gate for detecting said input vertical sync
signal by combining outputs of said counters.
7. A control device for power saving as claimed in claim 1, wherein said
vertical detected signal output means comprises:
a third monostable multivibrator providing a pulse signal in response to
the output of said vertical sync signal detecting means;
a flip-flop receiving said pulse signal from said third monostable
multivibrator as its clock signal, and outputting said vertical power-off
signal to said control output means;
a fourth monostable multivibrator providing a pulse signal in response to
said vertical sync signal outputted from said third flip-flop in said
vertical sync signal input means;
an inverter and an AND gate for resetting said flip-flop in accordance with
the output of said fourth monostable multivibrator.
8. A control device for power saving as claimed in claim 1, wherein said
control signal output means comprises:
an AND gate for AND-gating said horizontal power-off signal from said
horizontal detected signal output means and said vertical power-off signal
from said vertical detected signal output means, and outputting said
system power-off signal; and
an OR gate for OR-gating said horizontal power-off signal and said vertical
power-off signal, and outputting said suspension signal.
9. A control device for power saving as claimed in claim 1, wherein said
clock generating means comprises a decimal counter for performing decimal
counting with respect to said system clock signal, and providing its
counted output to said horizontal sync signal detecting means and said
vertical sync signal detecting means as their clock signal.
10. A control device for power saving as claimed in claim 1, wherein said
clock generating means comprises:
a 4:1 counter for counting said system clock signal and providing its
counted output to said horizontal sync signal detecting means as its clock
signal; and
an OR gate for OR-gating said input horizontal sync signal and the output
of said first monostable multivibrator in said horizontal detected signal
output means, and providing its output to said vertical sync signal
detecting means as its clock signal.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control device for power saving for
electric and electronic appliances such as personal computers, printers,
etc. which generates a suspension signal or a power-off signal to save
power by detecting a horizontal sync signal and a vertical sync signal
generated in the appliances.
2. Description of the Prior Art
Power saving is a function of electric or electronic appliances such as
personal computers, printers, etc. which can prevent unnecessary power
consumption by automatically putting the appliance in a power saving mode
if the appliance is not used for a predetermined time. Power saving may be
divided into a suspension mode for providing a power supply for a minimum
basic operation of the appliance and a power-off mode for intercepting the
power supply. In a personal computer, a processor provides to a control
device for power saving a horizontal sync signal and a vertical sync
signal being supplied to a monitor in a normal mode of operation if a key
signal is not entered for a predetermined time. Then, the control device
for power saving detects the sync signals and in combination of the sync
signals, provides to a central processing unit (CPU) a suspension signal
commanding the CPU to go into the suspension mode, or a power-off signal
commanding the CPU to go into the power-off mode.
FIG. 1 is a schematic circuit diagram of a conventional device for power
saving. Referring to FIG. 1, the conventional device is provided with a
diode D1 for clamping an input horizontal sync signal Hsync, transistors
Q1 and Q2 which are reversely turned on or off by the horizontal sync
signal Hsync inputted through the diode D1, a diode D6 for clamping an
input vertical sync signal Vsync, transistors Q4 and Q5 which are
reversely turned on or off by the vertical sync signal Vsync inputted
through the diode D6, diodes D2 to D5 and capacitors C2, C3, and C5 for
rectifying and smoothing outputs of the transistors Q1, Q2, Q4, and Q5,
and output transistors Q3, Q6 to Q8 which are controlled to be turned on
or off according to the rectified and smoothed output signals to provide a
suspension signal SUS or a power-off signal PO.
The numerals C1 and C4 denote coupling capacitors, R1 to R11 denote
resistors, and B+ denotes a power supply.
The operation of the conventional control device for power saving as
constructed above will now be explained.
Referring again to FIG. 1, if both the horizontal sync signal Hsync and the
vertical sync signal Vsync are inputted, the input horizontal sync signal
Hsync is clamped through the capacitor C1 and the diode D1, and the
clamped sync signal is applied to the transistors Q1 and Q2 through the
speed-up capacitor C6 and the resistor R1 to operate the transistors Q1
and Q2. The output of the transistor Q12 is rectified to a direct current
(DC) signal by the diodes D2 and D3 and the capacitors C2 and C3, and this
DC signal is applied to the transistors Q3 and Q7. The transistor Q3 is
turned on by the voltage rectified by the diode D2 and the capacitor C2,
while the transistor Q7 is turned on by the voltage rectified by the diode
D3 and the capacitor C3. If the transistor Q7 is turned on, the transistor
Q8 is turned off.
In the meantime, the input vertical sync signal Vsync is clamped through
the capacitor C4 and the diode D6, and the clamped sync signal is applied
to the transistors Q4 and Q5 through the resistor R6 to operate the
transistors Q4 and Q5. The output of the transistor Q5 is rectified by the
diodes D4 and D5 and the capacitors C3 and C5, and the rectified DC signal
is applied to the transistors Q6 and Q7. The transistor Q6 is turned on by
the DC voltage rectified by the diode D5 and the capacitor C5, causing the
suspension signal SUS to become low. Also, the transistor Q7 is turned on
by the DC voltage rectified by the diode D4 and the capacitor C3 and the
voltage rectified by the diode D3, causing the power-off signal PO to
become low. In this case, the system is in the normal mode.
In case that the horizontal sync signal Hsync is inputted, but the vertical
sync signal Vsync is not inputted, the transistor Q6 remains turned off,
resulting in that the transistor Q3 is turned off and the transistor Q7 is
turned on. Accordingly, the suspension signal SUS becomes high, while the
power-off signal PO becomes low, causing the system to go into the
suspension mode. On the contrary, in case that the horizontal sync signal
Hsync is not inputted, but the vertical sync signal Vsync is inputted, the
transistors Q4, Q5, and Q7 are all turned on, but the transistors Q3 and
Q6 are turned off. Accordingly, the suspension signal SUS becomes high,
while the power-off signal PO becomes low, causing the system also to go
into the suspension mode.
In case that neither the horizontal sync signal Hsync nor the vertical sync
signal Vsync is inputted, the transistors Q1 to Q3, and Q7 are turned off,
and the transistors Q4 to Q6 are turned off due to the absence of the
horizontal and vertical sync signals Hsync and Vsync. Since the transistor
Q7 is turned off, the transistor Q8 is turned on, and thus the suspension
signal SUS becomes low, while the power-off signal PO becomes high,
causing the system to go into the power-off mode.
However, the conventional control device for power saving as shown in FIG.
1 has the disadvantage that it has an inferior transient response
characteristic since it is constructed as an analog circuit. Further, the
initial operation of the conventional device becomes unstable due to the
capacitance of the capacitors employed in the circuit. This causes the
reliability of the power saving to deteriorate and integration of the
circuit to be difficult.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a control device for
power saving which enables integration of the circuit and improves its
transient response characteristic by constructing the device with a
digital circuit.
In order to achieve the above object, the control device for power saving
according to the present invention comprises:
horizontal sync signal input means for providing a horizontal sync signal
synchronized with a system clock signal;
horizontal sync signal detecting means for detecting whether or not said
horizontal sync signal is inputted by counting an output of said
horizontal sync signal input means;
horizontal detected signal output means for outputting a horizontal
power-off signal in accordance with an output of said horizontal sync
signal detecting means;
vertical sync signal input means for providing a vertical sync signal
synchronized with said system clock signal;
vertical sync signal detecting means for detecting whether or not said
vertical sync signal is inputted by counting an output of said vertical
sync signal input means;
vertical detected signal output means for outputting a vertical power-off
signal in accordance with an output of said vertical sync signal detecting
means;
control signal output means for outputting a system power-off signal or a
suspension signal for a suspension mode in accordance with said horizontal
power-off signal from said horizontal detected signal output means and
said vertical power-off signal from said vertical detected signal output
means; and
clock generating means for providing said system clock signal to said
horizontal sync signal detecting means and said vertical sync signal
detecting means.
BRIEF DESCRIPTION OF THE DRAWINGS
The above object and other features and advantages of the present invention
will become more apparent by describing the preferred embodiments thereof
with reference to the accompanying drawings, in which:
FIG. 1 is a schematic circuit diagram of a conventional control device for
power saving.
FIG. 2 is a schematic circuit diagram of the control device for power
saving according to one embodiment of the present invention.
FIGS. 3A to 3I are waveform diagrams related to the horizontal sync signal
at various points in FIG. 2.
FIGS. 4A to 4I are waveform diagrams related to the vertical sync signal at
various points in FIG. 2.
FIG. 5 is a schematic circuit diagram of the control device for power
saving according to another embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 2 shows a circuit of the control device for power saving according to
one embodiment of the present invention. The control device includes a
horizontal sync signal input section 100 for synchronizing an input
horizontal sync signal Hsync with a system clock signal CLK and outputting
the synchronized horizontal sync signal, a horizontal sync signal
detecting section 200 for detecting whether or not the horizontal sync
signal Hsync is inputted by counting the output of the horizontal sync
signal input section 100, and a horizontal detected signal output section
300 for outputting a horizontal power-off signal HPO in accordance with
the horizontal sync signal Hsync outputted from the horizontal sync signal
detecting section 200.
The control device also includes a vertical sync signal input section 400
for synchronizing an input vertical sync signal Vsync with the system
clock signal CLK and outputting the synchronized vertical sync signal, a
vertical sync signal detecting section 500 for detecting whether or not
the vertical sync signal Vsync is inputted by counting the output of the
vertical sync signal input section 400, and a vertical detected signal
output section 600 for outputting a vertical power-off signal VPO in
accordance with the vertical sync signal Vsync outputted from the vertical
sync signal detecting section 500.
The control device also includes a control signal output section 700 for
outputting a system power-off signal PO or a suspension signal SUS in
accordance with the horizontal power-off signal HPO and the vertical
power-off signal VPO, and a clock generating section 800 for generating
and providing the system clock signal to the horizontal sync signal
detecting section 200 and the vertical sync signal detecting section 500.
The horizontal sync signal input section 100 comprises a flip-flop 1 for
synchronizing the horizontal sync signal Hsync with the system clock
signal CLK, and a flip-flop 2 being toggled by the horizontal sync signal
Hsync synchronized by the flip-flop 1.
The horizontal sync signal detecting section 200 comprises counters 3 and 5
for counting the system clock signal CLK in a period when they are not
reset, the counters being reset by the output of the horizontal sync
signal input section 100, AND gates 4 and 6 for resetting the counters 3
and 5 in accordance with a system reset signal RESET and the non-inverting
output of the flip-flop 2 inputted thereto, AND gates 7 and 8 and an OR
gate 9 for detecting the input horizontal sync signal Hsync by combining
the outputs of the counters 3 and 5.
The horizontal detected signal output section 300 comprises a monostable
multivibrator 10 providing a pulse signal in accordance with the output of
the OR gate 9 in the horizontal sync signal detecting section 200, a
flip-flop 11 receiving the pulse signal from the monostable multivibrator
10 as its clock signal and outputting the horizontal power-off signal HPO
in accordance with the horizontal sync signal Hsync, a monostable
multivibrator 12 providing a pulse signal in accordance with the
horizontal sync signal Hsync outputted from the non-inverting terminal of
the flip-flop 1 in the horizontal sync signal input section 100, an
inverter 13 and an AND gate 14 for resetting the flip-flop 11 in
accordance with the output of the monostable multivibrator 12.
The vertical sync signal input section 400 comprises a flip-flop 15 for
synchronizing the vertical sync signal Vsync with the system clock signal
CLK, and a flip-flop 16 being toggled by the vertical sync signal Vsync
synchronized by the flip-flop 15.
The vertical sync signal detecting section 500 comprises counters 17 and 18
for counting the system clock signal in a period when they are not reset,
the counters 17 and 18 being reset by the output of the vertical sync
signal input section 400, AND gates 19 and 20 for resetting the counters
17 and 18 in accordance with the system reset signal RESET and the
inverting output of the flip-flop 16 inputted thereto, AND gates 22 and 23
and an OR gate 24 for detecting the input vertical sync signal Vsync by
combining the outputs of the counters 17 and 18.
The vertical detected signal output section 600 comprises a monostable
multivibrator 25 providing a pulse signal in accordance with the output of
the OR gate 24 in the vertical sync signal detecting section 500, a
flip-flop 26 receiving the pulse signal from the monostable multivibrator
25 as its clock signal and outputting the vertical power-off signal VPO in
accordance with the vertical sync signal Vsync, a monostable multivibrator
27 providing a pulse signal in accordance with the vertical sync signal
Vsync outputted from the non-inverting terminal of the flip-flop 15 in the
vertical sync signal input section 400, an inverter 28 and an AND gate 29
for resetting the flip-flop 26 in accordance with the output of the
monostable multivibrator 27.
The control signal output section 700 comprises an AND gate 30 for
AND-gating the horizontal power-off signal HPO from the horizontal
detected signal output section 300 and the vertical power-off signal VPO
from the vertical detected signal output section 600 and outputting the
system power-off signal PO, and an OR gate 31 for OR-gating the horizontal
power-off signal HPO and the vertical power-off signal VPO and outputting
the suspension signal SUS.
The clock generating section 800 comprises a decimal counter 21, which
performs decimal counting with respect to the system clock signal CLK, and
provides its output Q3 to the counters 3 and 5 and its output Q9 to the
counters 17 and 18.
The operation of the control device for power saving according to the
present invention as constructed above will be explained with reference to
FIGS. 2, 3A to 3I, 4A to 4I, and 5.
In case that both the horizontal sync signal Hsync and the vertical sync
signal Vsync are inputted, the control device is initialized, and then the
counter 21 in the clock generation section 800 performs decimal counting
with respect to the system clock signal. The output Q3 of the counter 21
is provided to the counters 3 and 5 as their clock signal, and the output
Q9 of the counter 21 is provided to the counters 17 and 18 as their clock
signal. Thus, the counters can operate with a timing synchronized with the
clock signal.
If the horizontal sync signal Hsync as shown in FIG. 3I is inputted to the
input terminal D of the flip-flop 1, the horizontal sync signal Hsync is
synchronized with the system clock signal CLK inverted by the inverter 32,
and the synchronized horizontal sync signal is provided from the output
terminal Q of the flip-flop 1 to the following flip-flop 2 as its clock
signal and to the monostable multivibrator 12 as its input data.
The flip-flop 2 is toggled by the horizontal sync signal Hsync, and outputs
a signal as shown in FIG. 3A and an inverted signal as shown in FIG. 3B.
The signal as shown in FIG. 3A, which is outputted from the non-inverting
output terminal Q of the flip-flop 2, is inputted to the reset terminal RS
of the counter 5 through the AND gate 6 to reset the counter 5, and the
inverted signal as shown in FIG. 3B, which is outputted from the inverting
output terminal Q* of the flip-flop 2, is inputted to the reset terminal
of the counter 3 through the AND gate 4 to reset the counter 3.
The counters 3 and 5 perform counting operation in a period when the reset
state is released (i.e., in a high-leveled period). At this time, if the
input horizontal sync signal Hsync exists, the outputs of the AND gates 7
and 8 are kept low as shown in FIGS. 3C and 3D since the reset-active time
of the AND gates 7 and 8 is determined to be shorter than the outputs Q2
and Q3 of the counters 3 and 5. Accordingly, the output of the 0R gate 9
becomes low as shown in FIG. 3E.
Since the output of the OR gate 9 is low, the present state does not
change, and thus the output of the monostable multivibrator 10 is not
generated as shown in FIG. 3F. Accordingly, the output of the flip-flop
11, which receives the output of the monostable multivibrator 10 as its
clock signal, is kept low as its initial reset state, causing the
horizontal power-off signal HPO to be low as shown in FIG. 3H. At this
time, the monostable multivibrator 12 receives the horizontal sync signal
Hsync outputted from the flip-flop 1 as its input data, and provides a
pulse signal. This pulse signal is inputted to the flip-flop 11 as its
reset signal through the inverter 13 and the AND gate 14 as shown in FIG.
3G. However, since the output of the flip-flop 11 has already been low,
the reset signal has no meaning.
The operation of the control device with respect to the input vertical sync
signal Vsync is the same as that with respect to the input horizontal sync
signal Hsync as described above.
If the vertical sync signal Vsync as shown in FIG. 4I is inputted to the
input terminal D of the flip-flop 15, the vertical sync signal Vsync is
synchronized with the system clock signal CLK, and the synchronized
vertical sync signal is inputted to the following flip-flop 16 as its
clock signal and to the monostable multivibrator 27 as its input data.
The flip-flop 16 is toggled by the input vertical sync signal Vsync, and
output a signal as shown in FIG. 4A and an inverted signal as shown in
FIG. 4B. The signal as shown in FIG. 4A, which is outputted from the
non-inverting output terminal Q of the flip-flop 16, is inputted to the
reset terminal RS of the counter 17 through the AND gate 19 to reset the
counter 17, while the inverted signal as shown in FIG. 4B, which is
outputted from the inverting output terminal Q* of the flip-flop 16, is
inputted to the reset terminal of the counter 18 through the AND gate 20
to reset the counter 18.
The counters 17 and 18 perform counting operation in a period when the
reset state is released (i.e., in a high-leveled period). At this time, if
the input vertical sync signal Vsync exists, the outputs of the AND gates
22 and 23 are kept low as shown in FIGS. 4C and 4D since the reset-active
time of the AND gates 22 and 23 is determined to be shorter than the
outputs Q6 and Q7 of the counters 17 and 18. Accordingly, the output of
the OR gate 24 becomes low as shown in FIG. 4E.
Since the output of the OR gate is low, the present state does not change,
and thus the output of the monostable multivibrator 25 is not generated as
shown in FIG. 4F. Accordingly, the output of the flip-flop 26, which
receives the output of the monostable multivibrator 25 as its clock
signal, is kept low as its initial reset state, causing the vertical
power-off signal VPO to be low as shown in FIG. 4H. At this time, the
monostable multivibrator 27 receives the vertical sync signal vsync
outputted from the flip-flop 15 as its input data, and provides a pulse
signal. This pulse signal is inputted to the flip-flop 26 as its reset
signal through the inverter 28 and the AND gate 29 as shown in FIG. 4G.
However, the output of the flip-flop 26 has already been low, and thus the
reset signal has no meaning.
Consequently, the horizontal power-off signal HPO outputted form the
flip-flop 11 and the vertical power-off signal VPO outputted from the
flip-flop 26 are inputted to the OR gate 31 and the AND gate 30 in the
control signal output section 700, resulting in that both the suspension
signal SUS and the power-off signal PO outputted from the control signal
output section become low.
In case that the horizontal sync signal Hsync is not inputted, but the
vertical sync signal Vsync is inputted, the counters 3 and 5 perform
counting operation with the clock signal provided from the counter 21 in a
period when the reset of the counters 3 and 5 is released. In response to
the outputs Q2 and Q3 of the counters 3 and 5, the outputs of the AND
gates 7 and 8 are shown in FIGS. 3C and 3D. Accordingly, the OR gate 9
outputs a signal as shown in FIG. 3E to the monostable multivibrator 10 as
its data.
The monostable multivibrator 10 outputs a pulse signal as shown in FIG. 3F
in accordance with the system clock signal CLK. Since the output of the
flip-flop 11, which receives the pulse signal from the monostable
multivibrator 10 as its clock signal, becomes high as shown in FIG. 3H in
a period when the horizontal sync signal Hsync does not exist, the
horizontal power-off signal HPO becomes high and thus the suspension
signal SUS outputted from the OR gate 31 becomes high.
Thereafter, if the horizontal sync signal Hsync is inputted, the monostable
multivibrator 12 generates a pulse signal in accordance with the
horizontal sync signal outputted from the flip-flop 1. This pulse signal
is provided to the flip-flop 11 through the inverter 13 and the AND gate
14 to reset the flip-flop 11, resulting in that the horizontal power-off
signal HPO and the suspension signal SUS may be low again.
In case that the horizontal sync signal Hsync is inputted but the vertical
sync signal Vsync is not inputted, the counters 17 and 18 perform counting
operation with the clock signal from the output terminal Q9 of the counter
21 in a period when the reset of the counters 17 and 18 is released, and
the outputs of the AND gates 22 and 23 are shown in FIGS. 4C and 4D in
accordance with the outputs Q2 and Q3 of the counters 17 and 18.
Accordingly, the OR gate 24 outputs the signal as shown in FIG. 4E to the
monostable multivibrator 25 as its input data, and the monostable
multivibrator 25 outputs the pulse signal as shown in FIG. 4F in
accordance with the system clock signal CLK.
The output of the flip-flop 26, which receives the clock signal from the
monostable multivibrator 25 as its clock signal, becomes high as shown in
FIG. 4H in a period when the vertical sync signal Vsync does not exist,
and thus the vertical power-off signal VPO becomes high, causing the
suspension signal SUS outputted from the OR gate 31 also to become high.
Thereafter, if the vertical sync signal Vsync is inputted, the monostable
multivibrator 27 outputs a pulse signal in accordance with the vertical
sync signal Vsync outputted from the flip-flop 15. This pulse signal is
provided to the flip-flop 26 through the inverter 28 and the AND gate 29
to reset the flip-flop 26, resulting in that both the vertical power-off
signal VPO and the suspension signal SUS may be low again.
In summary, if either the horizontal sync signal Hsync or the vertical sync
signal Vsync is inputted, either of the two power-off signals HPO and VPO
becomes high, resulting in that the suspension signal SUS outputted from
the OR gate 31 becomes high, and the system power-off signal PO outputted
from the AND gate 30 becomes low. In the meantime, neither the horizontal
sync signal Hsync nor the vertical sync signal Vsync is inputted, both the
horizontal power-off signal HPO and the vertical power-off signal VPO
become high, resulting in that both the suspension signal SUS and the
system power-off signal PO become high. The suspension signal SUS and the
system power-off signal PO as described above is provided to the following
control system such as a CPU, so that the control system controls the
appliance to go into the suspension mode or the system power-off mode.
FIG. 5 shows a circuit of the control device for power saving according to
another embodiment of the present invention. According to the circuit of
FIG. 5, the counter 21 in FIG. 2 is replaced by a 4:1 (divide-by-4)
counter 21a, and the output Q3 of this counter 21a is provided to the
counters 3 and 4 as their clock signal. Also, an OR gate 21b is added to
OR-gate the input horizontal sync signal Hsync and the output of the
monostable multivibrator 10. The output of the OR gate 21b is provided to
the counters 17 and 18 as their clock signal. Referring to FIG. 5, the
counter 21a counts the system clock signal CLK and provides its output
signal to the counters 3 and 5 as their clock signal as in FIG. 2. The OR
gate 21b provides the horizontal sync signal Hsync to the counters 17 and
18 as their clock signal if the horizontal sync signal Hsync is inputted.
If the horizontal sync signal Hsync is not inputted, the OR gate 21b
provides the output pulse signal of the monostable multivibrator 10 to the
counters 17 and 18 as their clock signal, enabling the counters 17 and 18
to operate. The counters 17 and 18 can store more than the 6:1
(divide-by-6) counted value.
From the foregoing, it will be apparent that the control device for power
saving according to the present invention has the advantages that its
transient response characteristic is improved and its control reliability
is greatly increased since it is constructed as a digital circuit, not as
an analog circuit as in the convention device, and the existence of the
input sync signal is determined within two-period time of the sync signal.
While the present invention has been described and illustrated herein with
reference to the preferred embodiments thereof, it will be understood by
those skilled in the art that various changes in form, details, and
applications may be made wherein without departing from the spirit and
scope of the invention.
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